Localized strip shape control and display

ABSTRACT

A localized strip shape rolling control system uses outputs from a plurality of tension measuring load cells mounted on a tension measuring roll to provide a localized display signal based on deviations from flatness. Control signals derived from each load cell output controls the lubricity at the roll by varying the supply of good and poor lubricants.

United States Patent 1191 1111 3,802,237 Albensi et al. Apr. 9, 1974 [54] LOCALIZED STRIP SHAPE CONTROL AND 3,213,655 10/1965 Reid 72/11 DISPLAY 3,210,982 10/1965 Polakowski.. 72 237 x 3,078,747 2/1963 Pearson 72/9 Inventors: Clarence Albensi; Edward J- Patula, 3,307,215 3/1967 Gerhard et al 18/2 both of Monroeville Borough; 2,674,127 4/1954 Garrett et al. 73/159 Richard L. Renner, Dravosburg; 3,324,695 6/1967 Sivilotti i 72/15 wm Roberts, Franklin Twp, 3,587,265 6/1971 Sivilotti 72/8 westmoreland county, an of p 3,496,744 2/1970 Mlzuno et al 72 12 [73] Assignee: United States Steel Corporation,

Pittsburgh, p Primary ExaminerMilton S. Mehr Attorney, Agent, or Firm-Rea C. Helm [22] F1led: May 26, 1972 [21] Appl. No.: 257,223

[57] ABSTRACT [5 2] Cl 72/ A localized strip shape rolling control system uses outputs from a plurality of tension measuring load cells g g i 2 43 mounted on a tension measuring roll to provide a lo- [5 e 0 ealc 172 2 00 203 calized display signal based on deviations from flatness. Control signals derived from each load cell output controls the lubricity at the roll by varying the [56] References Clted supply of good and poor lubricants.

UNITED STATES PATENTS 3,499,306 3/1970 Pearson 72/17 5 Claims, 6 Drawing Figures 88/1 64? I 5 2A CON TROL PATENTED APR 9 I974 SHEET 1 OF 3 520 lfza LOCALIZED STRIP SHAPE CONTROL AND DISPLAY This invention relates to the localized control of strip shape in a rolling mill and more particularly to continuously displaying and controlling deviations from flatness in rolled strip, such as steel, plastic, aluminum or the like, whenever the deviations result from a nonuniform longitudinal stress distribution.

When strip is subjected to nonuniform deformation conditions in the roll bite, internal stresses are created within the strip as longer over-rolled material attempts to line up with shorter under-rolled portions. In heavier gage material, the stresses may not be of sufficient magnitude to buckle the strip, but in the lighter gages of tinplate, plastic, aluminum and foil, it is more likely that the stresses will relieve themselves by buckling the strip on exit from the mill. The extent of the defect depends on the thickness of the strip and the amount of nonuniform deformation. However, in all cases where the strip is subjected to a sufficiently high tension so that the strip is essentially flat, a nonuniform tensile stress distribution will exist across the width of the strip. The longer over-rolled portions of the strip will be subjected to a lower tensile stress than the shorter under-rolled portions. Therefore, the degree of nonuniformity in the tensile stress distribution bears a direct relation to the degree of deviation from flatness that the strip will experience in the relaxed state.

The shape of rolled strip may be controlled by work roll bending, by backup roll bending or by thermally profiling the roll either by heating or cooling. Some of these methods only correct defects that are symmetrical with respect to the center line of the strip, others require very complex equipment, and some are very slow in response.

In accordance with our invention, a bridle roll with a plurality of tension measuring load cells provide periodic tension signals to a control circuit. The control circuit provides an output for display purposes based only on the relative deviations from flatness. A control signal, also based on relative deviations from flatness, is used for localized thermal control or localized lubricity control in the roll bite independent of any gage control system, or the average tension in the strip.

it is therefore an object of our invention to provide a localized strip shape display based on relative deviations from flatness.

Another object is to provide a localized strip shape rolling control system based on relative deviations from flatness by controlling the thennal profile of the rolls.

Still another object is to provide a localized strip shape rolling control system based on relative deviations from flatness by controlling the lubricity of the roll bite.

These and other objects will become more apparent after referring to the following specification and drawings in which:

FIG. 1 is a schematic perspective view of a cold rolled steel strip rolling mill with a roll for measuring the longitudinal tensile stress distribution across the strip width;

FIG. 2 is a control and display circuit for our inventron;

FIG. 3 is a schematic perspective view showing control by cooling;

FIG. 4 is a schematic diagram illustrating control by a single load cell by heating;

FIG. 5 is a schematic diagram illustrating control by single load cell by lubricity control of the roll bite; and

FIG. 6 is a schematic diagram illustrating an alternate control by a single load cell by lubricity control of the roll bite.

Referring now to the drawings, FIG. 1 shows a cold rolled steel strip rolling mill utilizing the features of our invention. Strip S is unwound from a supply coil 2, around entry bridle rolls 4 through work rolls 6, which may have backup rolls 8. After reduction in work rolls 6, the strip passes over a shape measuring roll 10, an exit bridle roll 12 and is recoiled onto a coil 14. Shape measuring roll 10 has a plurality, five are shown, of tension measuring cells A, B, C, D and E which through a slip ring assembly, 16 provide output signals 18A, 18B, 18C, 18D and 18E. The shape measuring roll is essentially the type shown in Atkins et al US. Pat. No. 3,668,578.

Referring now to FIG. 2, the control circuit of our invention, signal 18A from load cell A of FIG. 1 is connected to a differential amplifier 20A, such as a Model No. 3088/16 manufactured by the Burr-Brown Research Corporation, Tucson, Ariz. An output 22A of amplifier 20A is connected through a capacitor 24A to a rectifying circuit 26A. An output 28A of circuit 26A is connected to an input of an operational amplifier 30, such as a Model No. 3044/15 manufactured by Burr- Brown Corporation, Tucson, Arizona, through a summing resistor 32A. The other four load cells, B, C, D and E of FIG. 1, are also each connected to amplifier 30 through an amplifier, a capacitor and a rectifier, similar to 20A, 24A and 26A, respectively, through a resistor 32B, 32C, 32D and 32E each having the same value of resistance as resistor 32A. Amplifier 30 has a feedback resistor 34 having one-fifth the value of resistor 32A.

Amplifier 30 has an output 36 connected through a resistor 38 to an input of an operational amplifier 40A which may be a Model No. 3044/15 manufactured by Burr-Brown Corporation, Tucson, Ariz. Output 28A is also connected to an input of amplifier 40A through a resistor 42A. Amplifier 40A has an output 44A connected to an input of a display unit 46. Display unit 46 has other inputs 44B, 44C, 44D and 44B which are derived from signals 18B, 18C, 18D and 18E, respectively, in the same manner as signal 18A. Display unit 46 may be a Brush recorder, a multiplex oscilloscope or a plurality of vertical ribbon meters.

Signals 28A and 36 are also connected to inputs of an operational amplifier 48A, such as a Model No. 1510/25 manufactured by Burr-Brown Corporation, Tucson, Ariz. Outputs of amplifier 48A are connected to inputs of a comparator 50A, such as a Model No. 9872/25 manufactured by Burr-Brown Corporation, Tucson, Ariz. Comparator 50A has an output 52A connected through a resistor 54A and a diode 56A connected to ground. Similar connections with similar components provide outputs 52B, 52C, 52D and 52E from the load cells B, C, D and E in roll 10.

Under optimal conditions, internal stresses are evenly distributed throughout the strip and the normal reaction tensile loading force of strip S on roll 10 is carried evenly distributed across the face of roll 8. The strip will remain flat when tension is removed. If the strip is rolled so as to develop uneven internal stresses, such as loose or over-rolled sections, those sections will carry less of the normal reaction tensile loading on roll than tight or under-rolled sections. As the strip passes over load cells A, B, C, D and E, the differences in tensile loadings will produce different signals 18A, 18B, 18C, 18D and 18E. The differences between the signals indicate the relative degree of flatness of strip S as it passes over roll 10. Since the load cells A, B, C, D and E will contact the strip for only a portion of each revolution of roll 10, the signal generated will be periodic with a frequency dependent on the angular velocity of the roll 10. The centripetal forces on the load cells A, B, C, D and E due to rotational effects, and any forces due to the manner of assembly or the particular configuration of a load transfer pin between the strip and a load cell will generate a d-c voltage once a steady-state operating speed is reached. Therefore, the a-c components in signal 18 from load cells A, B, C, D and E provide all the information concerning tensile stress.

Signal 18A is amplified in amplifier 20A and the d-c component is decoupled by capacitor 24A. The signal from capacitor 24A is then rectified in circuit 26A which may be a conventional diode bridge. This provides a d-c signal 28A which is proportional to the value of local tension. Signals 28A, 28B, 28C, 28D and 28E are then averaged by the use of amplifier 30 and matching resistors 32 and 34 to provide an average signal 36. Each signal 28A, 28B, 28C, 28D and 28E is then individually compared with the average signal 36 and the difference, signal 44A, 44B, 44C, 44D and 44E are displayed on unit 46. Thus the display system does not depend upon the absolute value of the tension, but only the relative value of the tension. Indicator 46 shows the relative strip tension, which is developed independent of rolling force measurement or gage of the strip.

While the signals 44A through 44E could be used for control purposes, the signals are more useful if modified as shown by the remainder of the circuit in FIG. 2. Signals 28A and 36 are amplified and connected to comparator 50A. The output from comparator 50A is a positive 6 volts where signal 28A is greater than signal 36 and a negative 6 volts when signal 36 is greater than signal 28A. By use of diode 56A the latter signal is changed to 0 volts. The signals thus developed are relative signals and do not depend upon the absolute value of strip tension or the overall average strip tension and therefore are independent of the average strip tension and are compatible with other components.

Referring now to FIG. 3, one method of controlling strip shape using the signals 52A through 52E is by cooling of the rolls. A source of coolant, such as water, 58 is fed by a pump 60 to a plurality of controlled spray heads 62A, 62B, 62C, 62D and 62E positioned to spray upper roll 8 at a location corresponding to the respective load cells in roll 10. The signals 52A, 52B, 52C, 52D and 52B from control circuit 64 shown in FIG. 2 are connected to their respective spray heads 62 to control the spray. When signal 52A is at 6 volts, or the local tension is less than the average tension, the controlled spray head, controlled by a valve, such as a Red Hat Model No. 82l0-C4 manufactured by Asco Valves, Automatic Switch Company, Florham Park, N.J., opens to permit 100 percent of the supply flow rate to flow through the spray head 62A. When signal 52A is returned to 0 volts, or the local tension is greater than the average tension, the valve in spray head 62 changes to a partly closed position, for example to a 20 percent flow rate which may be the minimum flow rate required for adequate cooling. While the spray heads 62 are shown on upper backup roll 8, obviously the spray heads could be located on the bottom backup roll 8 or either or both of the work rolls 6.

In FIG. 4 which shows the shape control associated with load cell A, control signal 52A from control circuit 64 is used in another manner. Reference numeral 66 represents a source of heating gas, such as natural gas. Source 66 is connected to a series of valves, one associated with each load cell, valve 68A is shown. Such valves may each be a Red Hat Model No. 8210- C4. Valve 68A supplies gas to a burner 70A which supplies localized heat to lower roll 8. Other possible burner locations are shown at 72 including the strip itself if desired. If the local reaction force exceeds the average value, valve 66A is opened to allow heat to be applied to the roll. If the local value of strip reaction force is less than the average force, the valve remains closed and no heat is applied. While only the burner and valve associated with load cell A is shown, there are additional burners and valves associated with each load cell. Localized heating the strip before entry into the rolls changes its flow stress characteristics and makes this method more effective.

In FIG. 5 which shows the shape control associated with load cell A, the control signal 52A from control circuit 64 is used to control the rolling lubricant used in rolling strip S. A source of rolling lubricant 74 is connected to a valve 76A which may be a Red Hat Model No. 82l0-C4 manufactured by Asco Valves, Automatic Switch Company, Florham Park, NJ. Valve 76A is controlled by signal 52A open at a 6 volt signal and closed at a 0 volt signal to control the flow of lubricant to spray heads 78 shown lubricating lower roll 6, lower roll 8 and strip S. Other locations, 80, are shown on the upper side of the roll. Any combination of spray heads may be used, depending upon the nature of the rolling operation and the material being rolled. Valve 76A may also be set so that in the off signal position the minimum lubricant is being supplied.

FIG. 6 illustrates a dual spray or mist lubricant control system. The system is shown only with respect to load cell A. A supply of a good lubricant, 82, such as a vegetable or animal fatty oil, is connected to a control valve 84A, such as Red Hat Model No. 82l0-C4 which is normally closed when signal 52A is at 0 volts. A supply of a poor lubricant, 86, such as kerosene, is connected to a control valve 88A, such as a Red Hat Model No. 82l0-C 14 which is normally open when signal 52A is at 0 volts. Valves 84A and 88A are connected to a spray head 90A shown as supplying lubricant at the roll bite at lower roll 6. Other locations such as at 92 may also be used to supply the lubricant. If signal 52A changes from 0 volts to 6 volts, valves 84A and 88A will both change supplying a different quality of lubricant to the rolling operation. One or both of valves 84A and 88A may also be set so that in the off position a minimum flow of a lubricant is maintained.

The system operates independently of any gage controls and provides localized shape control independent of the average tension across the strip. While a tension measuring roll with five load cells is shown, obviously any number could be used depending upon the degree of localized control desired. The system corrects asymmetrical as well as symmetrical deviations from flatness. While the Atkins et al. device is preferred to supply local tension signals, other devices providing periodic signals proportional to strip tensile stress could also be used, as for example, individual rollers on hot rolled material.

We claim: 1. A localized strip shape rolling control system for a rolling mill having means for providing a plurality of periodic signals proportioned to strip tensile stresses with each signal being associated with one of a plurality of longitudinal local measuring locations comprising an averaging circuit connected to said means for providing a plurality of periodic signals for providing an average of said plurality of signals, means connected to said averaging circuit and said means for providing a plurality of periodic signals for comparing the averaging circuit output with the periodic signal associated with each measuring location and providing a first control signal for each measuring location when said averaging circuit output is greater and a second control signal for each measuring location when said periodic signal is greater, a source of a first rolling lubricant, a source of a second rolling lubricant, said second lubricant having a rolling lubrication characteristics inferior to the rolling lubrication characteristics of the first lubricant,

a plurality of distribution systems connected to said sources of lubricants and arranged to supply both lubricants to said rolling mill at each measuring location and a plurality of control valves for supplying at each measuring location said first lubricant responsive to said first control signal and said second lubricant in response to said control signal.

2. A system according to claim 1 which includes means connected to said averaging circuit and said means for providing a plurality of periodic signals for determining the difference between the output of the averaging circuit and each periodic signal associated with a measuring location and means for displaying the difference between the output of the averaging circuit and each periodic signal.

3. A system according to claim 2 in which said means for displaying differences is a chart recorder.

4. A system according to claim 2 in which said means for displaying differences is a voltmeter.

5. A system according to claim 2 in which said means for displaying differences is an oscilloscope. 

1. A localized strip shape rolling control system for a rolling mill having means for providing a plurality of Periodic signals proportioned to strip tensile stresses with each signal being associated with one of a plurality of longitudinal local measuring locations comprising an averaging circuit connected to said means for providing a plurality of periodic signals for providing an average of said plurality of signals, means connected to said averaging circuit and said means for providing a plurality of periodic signals for comparing the averaging circuit output with the periodic signal associated with each measuring location and providing a first control signal for each measuring location when said averaging circuit output is greater and a second control signal for each measuring location when said periodic signal is greater, a source of a first rolling lubricant, a source of a second rolling lubricant, said second lubricant having a rolling lubrication characteristics inferior to the rolling lubrication characteristics of the first lubricant, a plurality of distribution systems connected to said sources of lubricants and arranged to supply both lubricants to said rolling mill at each measuring location and a plurality of control valves for supplying at each measuring location said first lubricant responsive to said first control signal and said second lubricant in response to said control signal.
 2. A system according to claim 1 which includes means connected to said averaging circuit and said means for providing a plurality of periodic signals for determining the difference between the output of the averaging circuit and each periodic signal associated with a measuring location and means for displaying the difference between the output of the averaging circuit and each periodic signal.
 3. A system according to claim 2 in which said means for displaying differences is a chart recorder.
 4. A system according to claim 2 in which said means for displaying differences is a voltmeter.
 5. A system according to claim 2 in which said means for displaying differences is an oscilloscope. 